1. Field of the Invention
The present invention relates to a pointing device for a computer system with automatic detection of lifting and to a relative control method.
2. Description of the Related Art
As is known, by now all computer systems and other electronic apparatuses equipped with graphic interface are provided with pointing devices, which enable the user to interact in an extremely simple and intuitive way. The most widespread pointing device, namely, the mouse, is provided with a shell, within which a motion transducer is housed. The shell is gripped and translated by the user, generally along a horizontal sliding surface, and the motion transducer sends signals indicating the path followed by the mouse to the computer system. The signals are then processed by the computer system for updating the position of a cursor displayed by the graphic interface. Normally, the mouse is also equipped with one or more pushbuttons, which the user can use for issuing further commands to the computer system.
As regards the movement transducer, different solutions have been proposed. Amongst the most recent and most promising ones, is the use of inertial sensors, in particular two-axes accelerometers made using MEMS (micro-electro-mechanical systems) technology, which detect the accelerations impressed to the mouse by the user along a sliding surface (hereinafter, mice based upon inertial sensors will, for reasons of simplicity, be referred to as “inertial mice”, just as the term “optical mice” is commonly applied to mice that use optical motion transducers). The data regarding accelerations are supplied to a processing unit and integrated in time a first time and a second time, for calculating the instantaneous velocity and the instantaneous position of the mouse, respectively.
A drawback, which regards in particular, but not exclusively, inertial mice, occurs when the user needs to displace the mouse itself without the cursor displayed on the screen of the computer system being moved accordingly (for example, because the mouse has reached an edge of the purposely provided mouse-pad on which it is resting, or in any case the space available in one direction has been used up). Whereas, in the case of optical or electromechanical mice, the movement transducer must necessarily be in contact with or at least in the proximity of the surface of sliding and does not work when it is separated therefrom, inertial sensors continue to operate even when the mouse is lifted. It is therefore not possible, with simple operations, to recover space of maneuver for the user, without moving the cursor displayed by the computer system. In effect, also mice with optical or electromechanical movement transducers are not altogether immune from the problem described, even though they are less sensitive. In fact, an optical movement transducer not correctly coupled to the sliding surface of the mouse in any case receives light stimuli that could be wrongly interpreted. In an electromechanical movement transducer, sliding is possible between the mechanical parts (balls, rollers) even when the mouse is picked up from the sliding surface.